From “Woe to Recovery”, it sounds like the title of a book or film
Where do I start, when assembling the cylinders, one of the jobs was to drill out the valve guides. When I drilled the first one I managed to break a drill bit of in the middle of it. I attempted to get it out by cutting off the rear spigot and drilling small holes around the end of the drill bit but didn’t succeed in getting it out. I popped a bit of rod in the other end and it went a fair way in so I reasoned that I might get away with shortening the rod because the valve stems don’t appear to move that much.
This was what was peeking out of the end of the casting but it wasn’t quite enough to grip.
When I broke the drill bit off in the first casting, I decided to make a collet to allow me to better grip the second casting without damage and I was able to drill the second one without issue.
This is the collet and another view of my attempts to remove the offending drill bit stub
DJH Streamlined Coronation – Motion – Getting out of trouble with a broken drill bit in a whitemetal casting
I advised the gent that I am building it for what had happened and that we may need a spare casting but I was going to attempt to work my way past it. During the assembly of the valve gear I carefully measured the amount of valve stem and progressively shortened it until it fit.
Fast forward to giving it a test run and it dropped out of the guide jamming up the valve gear.
When this happened on Tuesday evening I took the wise course and stopped to ponder.
First thing yesterday morning as I was getting up for work, Chris said I have the solution to getting the drill bit out and proceeded to explain the idea that she had dreamt while asleep. The idea was basically, to cut a cut down the side of the casting to relieve the grip from the whitemetal and then drift the stub out.
After dinner I went into the workshop to take the valve gear to bits and unsolder the valve guide casting. I then out the casting in the collet and after a bit of a fiddle managed to get the seam of the casting lined up with the slit in the collet and gripped in the vice.
That done and using an old Exacto Blade, I proceeded to cut through the side of the casting using some odour free white spirit as a lubricant (made more essential by the fact that this Exacto blade has a slight kink at one end). I kept steadily cutting until I felt the blade grating on the side of the drill bit stub (why I used an old blade) and then removed the casting from the vice.
The next bit’s I forgot to take photos of but using another broken drill bit as a drift I placed the bottom end of the casting on a block of wood which I have on my bench with the protruding stub of the drill over a hole that I had drilled when going through something previously (it doesn’t quite look like swiss cheese but there are a good few holes in it).
The drift moved the drill bit out a few millimetres further, to the point where I was able to grip it in a pin vice. I was then able to grip the casting in my hand and a twist of the pin vice had it free.
I then filled the seam with 70 degree solder and using the collet as a heat sink I soldered the casting back on and cleaned it up. In the photo below the seam is uppermost and is to all intents and purposes invisible.
Lastly I dismantled and remade the valve stem. The original is two layers of etch. I made the replacement from a piece of 1.10mm brass rod. I am not too happy with the boss so I plan to have another go later this morning.
This is the shortened version.
This is with the bit that I had cut off
Lastly this is the replacement.